1. Field of the Invention
The invention relates to a catalyst for removing nitrogen oxides, carbon monoxide, or hydrocarbons from exhaust gases by use of metal phthalocyanines which are treated with NO and O.sub.2, and to a method of preparing such a catalyst.
2. Description of the Prior Art
Such a catalyst and a method of that kind are known from DE-PS 27 43 03).
In the face of the state of the art, the object ensues of developing the known catalyst such that an entrainment or blowing out of the active component in strong gas currents will be prevented, that the specific activity of the catalyst will be improved by a great surface, and that diminishing of the activity by particle abrasion will be prevented.
The object is met, in accordance with the invention, by catalysts for removing nitrogen oxides, carbon monoxide, and/or residual hydrocarbons from exhaust gases, which catalysts are obtainable by treating metal phthalocyanines with NO and/or O.sub.2 at elevated temperatures, and characterized in that, prior to being treated with NO and/or O.sub.2, metal phthalocyanines are applied onto or into a carrier, and that subsequently the carrier is treated with nitrogen oxides and/or mixtures of nitrogen oxide and carbon monoxide and/or with oxygen and/or mixtures of oxygen and carbon monoxide or with nitrating or oxidizing gases or vapors at temperatures above 120.degree. C. or with nitrating or oxidizing solutions.
This catalyst as well as methods of making the same and special modifications thereof are characterized in the claims and specification.
In accordance with certain aspects of the invention, a catalyst for removing nitrogen oxides, carbon monoxide, residual hydrocarbons and mixtures thereof from exhaust gases is provided in which the catalyst is prepared by the steps of:
(a) impregnating a carrier with a metal phthalocyanine; and
(b) subsequently treating the carrier with a member selected from the group consisting of (i) nitrating gases at a temperature above 120.degree. C., (ii) oxidizing gases at a temperature about 120.degree. C. (iii) mixtures of nitrating and oxidizing gases at a temperature above 120.degree. C., (iv) nitrating solutions, and (v) oxidizing solutions.
In certain embodiments of the invention, prior to step (b), a transition metal oxide is applied to the carrier, either prior to or simultaneously with the impregnation of the carrier with the metal phthalocyanine.
The entrainment or blowing out of the active component in case of strong gase currents is prevented by virtue of the intimate mixing or combining of catalyst and carrier produced in accordance with the invention. The large surface of the carrier raises the specific activity of the catalysts, while the embedding of the active catalysts, totally or partly penetrating the carrier volume, prevents a lessening of the activity by particle abrasion. Furthermore, it was observed that the catalytic activity of the active component is enhanced by the chemical and/or physical interaction between catalyst and carrier.